HDU 5876 Sparse Graph （补图BFS） 2016 ACM/ICPC Asia Regional Dalian Online

题目点我点我点我

题目大意：给你一个图和点s，求s在补图中到其他各点的最短距离。

解题思路：补图的经典做法，BFS。利用set插入删除操作。

/* ***********************************************┆  ┏┓　　　┏┓ ┆┆┏┛┻━━━┛┻┓ ┆┆┃　　　　　　　┃ ┆┆┃　　　━　　　┃ ┆┆┃　┳┛　┗┳　┃ ┆┆┃　　　　　　　┃ ┆┆┃　　　┻　　　┃ ┆┆┗━┓　马　┏━┛ ┆┆　　┃　勒　┃　　┆　　　　　　┆　　┃　戈　┗━━━┓ ┆┆　　┃　壁　　　　　┣┓┆┆　　┃　的草泥马　　┏┛┆┆　　┗┓┓┏━┳┓┏┛ ┆┆　　　┃┫┫　┃┫┫ ┆┆　　　┗┻┛　┗┻┛ ┆************************************************ */#include <stdio.h>#include <string.h>#include <iostream>#include <algorithm>#include <vector>#include <queue>#include <stack>#include <set>#include <map>#include <string>#include <math.h>#include <stdlib.h>#include <bitset>using namespace std;#define rep(i,a,b) for (int i=(a),_ed=(b);i<=_ed;i++)#define per(i,a,b) for (int i=(b),_ed=(a);i>=_ed;i--)#define pb push_back#define mp make_pairconst int inf_int = 2e9;const long long inf_ll = 2e18;#define inf_add 0x3f3f3f3f#define mod 1000000007#define LL long long#define ULL unsigned long long#define MS0(X) memset((X), 0, sizeof((X)))#define SelfType intSelfType Gcd(SelfType p,SelfType q){return q==0?p:Gcd(q,p%q);}SelfType Pow(SelfType p,SelfType q){SelfType ans=1;while(q){if(q&1)ans=ans*p;p=p*p;q>>=1;}return ans;}#define Sd(X) int (X); scanf("%d", &X)#define Sdd(X, Y) int X, Y; scanf("%d%d", &X, &Y)#define Sddd(X, Y, Z) int X, Y, Z; scanf("%d%d%d", &X, &Y, &Z)#define reunique(v) v.resize(std::unique(v.begin(), v.end()) - v.begin())#define all(a) a.begin(), a.end()typedef pair<int, int> pii;typedef pair<long long, long long> pll;typedef vector<int> vi;typedef vector<long long> vll;inline int read(){int ra,fh;char rx;rx=getchar(),ra=0,fh=1;while((rx<'0'||rx>'9')&&rx!='-')rx=getchar();if(rx=='-')fh=-1,rx=getchar();while(rx>='0'&&rx<='9')ra*=10,ra+=rx-48,rx=getchar();return ra*fh;}//#pragma comment(linker, "/STACK:102400000,102400000")const int N = 2e5 + 5;struct Edge{    int to,nx;}edge[N*2];int head[N],cnt;void addedge(int u,int v){    edge[cnt] = Edge{v,head[u]};    head[u] = cnt++;}int n,m,dis[N];void bfs(int s){    set<int>s1;    set<int>s2;    set<int>::iterator it;    for(int i=1;i<=n;i++)    {        if(i!=s)s1.insert(i);    }    queue<int>q;    dis[s] = 0;    q.push(s);    while(!q.empty())    {        int u = q.front();        q.pop();        for(int i=head[u];i;i=edge[i].nx)        {            int v = edge[i].to;            if(!s1.count(v))continue;            s1.erase(v);            s2.insert(v);        }        for(it=s1.begin();it!=s1.end();it++)        {                dis[*it] = dis[u] + 1;                q.push(*it);        }        s1.swap(s2);        s2.clear();    }}int main(){//freopen("in.txt","r",stdin);//freopen("out.txt","w",stdout);ios::sync_with_stdio(0);cin.tie(0);int t;t= read();while(t--)    {        n = read(), m = read();        MS0(head);        memset(dis,inf_add,sizeof dis);        cnt = 1;        for(int i=1;i<=m;i++)        {            int u,v;            u = read(), v = read();            addedge(u,v);            addedge(v,u);        }        int s;        s = read();        bfs(s);        for(int i=1;i<=n;i++)        {            if(i==s)continue;            if(dis[i]==inf_add)dis[i] = -1;            printf("%d",dis[i]);            if(i==n)printf("\n");            else printf(" ");        }    }return 0;}